Naphthalenes radical ions

Tri-(l-naphthyl)phosphine is cleaved by alkali metals in THF solution. " Reaction with sodium gives the naphthalene radical-ion, with lithium the perylene radical-ion, and with potassium the radical-ion (22). Hydrocarbon radical-ion formation was thought to occur via naphthalene derived from the metal naphthalenide. E.s.r. spectra of further examples of phosphorus-substituted picrylhydrazyl radicals have been reported. ... 

Complications resulting from kjk > 1 may be responsible for the observations of Lyssy (34) who found deviations in the molecular weights of anionically polymerized styrene from the theoretically expected value of Mtotaljl0 when the degree of polymerization was very low. In the discussion of his results he implies that the initiation is slow, and indeed, he was able to demonstrate the presence of naphthalene- radical-ions in the solution of living polystyrene. The work of Levy and Szwarc (35) leads to similar conclusions. 

A full report has been published describing the light induced reaction of naphthalene with carbon dioxide in DMF containing amines to give a- and j8-naphthoic acids.The reaction most likely occurs by electron transfer from the amine to the naphthalene excited state followed by coupling of the naphthalene radical ion with carbon dioxide. 

The catalyst is prepared by the reaction of sodium metal with naphthalen( and results in the formation of a radical ion ... 

Besides a parent ion, the mass spectra of benzo- and dibenzothiepins show the corresponding naphthalene or phenanthrene radical cations as the base peak.2-16 The mass spectra of 1-benzo-thiepin 1-oxides and 1,1-dioxides show the same naphthalene radical cation, formed by loss of sulfur monoxide or sulfur dioxide, respectively.14 In contrast, in the mass spectrum of 2,7-di-terf-butylthiepin peaks resulting from the loss of sulfur are not found.17... 

In complex organic molecules calculations of the geometry of excited states and hence predictions of chemiluminescent reactions are very difficult however, as is well known, in polycyclic aromatic hydrocarbons there are relatively small differences in the configurations of the ground state and the excited state. Moreover, the chemiluminescence produced by the reaction of aromatic hydrocarbon radical anions and radical cations is due to simple one-electron transfer reactions, especially in cases where both radical ions are derived from the same aromatic hydrocarbon, as in the reaction between 9.10-diphenyl anthracene radical cation and anion. More complex are radical ion chemiluminescence reactions involving radical ions of different parent compounds, such as the couple naphthalene radical anion/Wurster s blue (see Section VIII. B.). 

The importance of radical ions and electron-transfer reactions has been pointed out in the preceding sections (see also p. 128). Thus, in linear hydrazide chemiluminescence (p. 103) or acridine aldehyde or ketone chemiluminescence, the excitation steps consist in an electron transfer from a donor of appropriate reduction potential to an acceptor in such a way that the electron first occupies the lowest antibonding orbital, as in the reaction of 9-anthranoyl peroxide 96 with naphthalene radical anion 97 142> ... 

A general theory of the aromatic hydrocarbon radical cation and anion annihilation reactions has been forwarded by G. J. Hoytink 210> which in particular deals with a resonance or a non-resonance electron transfer mechanism leading to excited singlet or triplet states. The radical ion chemiluminescence reactions of naphthalene, anthracene, and tetracene are used as examples. 

Radical ion pairs also react by proton, atom, or group transfer. We illustrate proton transfer in reactions of aromatic hydrocarbons with tertiary amines. These reactions cause reduction or reductive coupling. In the reduction of naphthalene, the initial ET is followed by H" transfer from cation to anion, forming 67 paired with an aminoalkyl radical the pair combines to generate... 

The electron spin resonance (ESR) spectra of the radical ions of 230 indicate there are no large deviations from the free-electron g value that would have been expected had the 3d orbitals of the sulfur atom played an important part in influencing the spin density of the molecule. Consequently, structure 230 may not be the main contributor to the electronic structure of the compound. Such stability in this compound could be attributed to the inertness of the NSN group and the presence of the aromatic naphthalene ring. However, the H-NMR chemical shifts (8 = 4.45 ppm) suggest the compound is antiaromatic. The compound is therefore referred to as an ambiguous aromatic compound (78JA1235). 

Reduction of trichloroethylene by a series of well-characterized outer-sphere electron-transfer reagents, viz. the radical anions of naphthalene, pyrene, perylene, decamethylcobaltocene, and cobaltocene, resulted in the formation of cis- and trans-dichloroethylene in ratio varying from 0.87 to 4.5, whereas in the reduction by vitamin B12, the ratio was 30 1. This indicated that reduction with vitamin B12 occurs with a non-outer-sphere electron-transfer mechanism. A mechanism involving initial formation of a radical ion followed by an ejection of a chloride to give d.v-dichlorovinyl radical and franx-dichlorovinyl radical has been proposed.284... 

In 1983, Rentzepis published a paper [38] dealing with the charge-transfer interaction of chloranil (9) and aromatic hydrocarbons, e.g. naphthalene (11). Nanosecond spectroscopy of this system [39] could verify some intermediates of the proposed mechanism [21, 40] (Scheme 3) that is the triplet excited acceptor and the free solvated radical ions (A- )s and (D+ ),. 

As acceptors, they used 9,10-dicyanoanthracene (DCA) or 2,6,9,10-tetracyanoan-thracene (TCA), the donors were methylated benzenes or naphthalenes. The D/A pair was designed to give radical ion pairs on irradiation. In order to determine sep, they monitored the quantum yield of dimethoxystilbene radical cation formation [70], which intercepts the free radical cation of the donor exclusively. Assuming a constant k, from earlier studies [66b], they indirectly obtained k e, according to Eq. (11) ... 

Their controlled formation can be utilized to control the course of the chemical reaction. In this context the chiral discrimination of PET processes of a chiral electron acceptor and (pro)chiral electron donors is of special interest We have observed such a discrimination in case of the isomerization of 1,2-diary Icyclo-propanes [122] and, for the first time, in case of a bimolecular PET process, e.g. the dimerization of 1,3-cyclohexadiene in presence of (+) and (—) l,l -bi-naphthalene-2,2 -dicarbonitrile as chiral electron acceptors [123]. Experiments in the same field are undertaken by Schuster and Kim and have been published recently [124], So far the enantiomeric excesses are small (ca. 15% [124] in toluene at —65 °C) but future efforts will certainly give more information about the applicability of catalytic asymmetric PET reactions. Consequently, the conditions which govern the formation and the fate of radical ion pairs are of central importance both for a better understanding of the mechanism and for synthetic applications. 

In contrast to the observed reactivity of phenoxide and aryl alkoxide ions, arene and heteroarene thiolate ions typically couple with aryl radical to generate C—S bonds. The only exception to this regioselective reaction is the addition of 1-naphthalene thiolate ion to p-anisyl radical to render both C- and S-substitutions in 14% and 65% yields, respectively, while with 1-naphthyl radical, 95% of C—S coupling is obtained. In general, PhS- ions react with Arl in liquid ammonia under photostimulation to afford good yields of ArSPh or heteroaryl-SAr (70-100%). Substitution of the less-reactive ArBr can be achieved under photochemical initiation in DMF, MeCN, or DM SO [1],... 

Fig. 4. Back electron transfer rates in photogenerated radical ion pairs in acetonitrile. In all cases cyanoanthracenes served as electron acceptors in their excited states, (a) Methylated benzene derivatives [60b] as donors (one-ring compounds), V = 11.5 cm"1, As = 1.63 eV. (b) Methylated biphenyls or naphthalenes [60b] as donors (two-ring compounds), V = 8.5 cm-1, /, = 1.48 eV. (c) Methylated phenanthrenes [60b] as donors (three-ring compounds) V = 8.0 cm-1, Xs = 1.40 eV. (dl Diphenylbutadienes [61] as donors, V = 8 cm-, X, = 1.55 eV. In all cases X, = 0.25 eV and V= 1500 cm-1...

The SIFT group of Bierbaum at the University of Colorado has also recently been active in the field of ion/atom chemistry, as a facet of their exploration of the IS chemistry of PAH cations. Rate coefficient measurements for reactions of the naphthalene radical cation, C10HJ, the closed shell naphthylium cation,... 

KdisR. Ac+ are the dissociation constants of the ion pairs Rf Ac+ and R Ac+. Under suitable conditions, the equilibria (29)—(31) can be followed by spectro-photometric methods [167c, 169], There exist some very important specific reactions of the type shown in eqns. (29) and (30) which are poorly characterized. This concerns, for example, the electron transfer from naphthalene- metal+ (Szwarc initiator) to styrene or other monomers [see Chap. 3, eqn. (46)]. The rapid consecutive reactions of the styrene radical ion make a direct measurement of the equilibrium impossible. Indirect data are not reliable. 

Wilkinson and Schroeder (1979) have shown that the triplet states of aromatic hydrocarbons are quenched by quinones, the efficiency of quenching being related to the electron affinity of the quinone and the ionisation potential of the triplet hydrocarbon (Schroeder and Wilkinson, 1979). It was concluded that the quenching did not involve full electron transfer in nonpolar solvents. Photolysis experiments have shown that in propionitrile tetrachloro-benzo-l,4-quinone reacts with naphthalene to give radical ions (Gschwind and Haselbach, 1979). The naphthalene radical cation reacts with naphthalene to give a detectable intermediate. 

Many aromatic compounds can undergo one-electron reduction by alkali metals, such as Na and Li. For example, the reaction of naphthalene with sodium in an aprotic solvent gives the naphthalene radical anion - sodium ion salt. 

Magnesium reacts with naphthalene and higher polycyclic aromatics in liquid aimnonia or HMPA to form the radical ion. Adducts with anthracene and substituted anthracenes form in THF. Depending upon substitution and conditions, they have a variety of structures. The l,10-bis(trimethylsilyl) compound had structure (47) in the crystal, with magnesium bridging the 1,10-positions (C-Mg =... 

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